1. Field of the Invention
The invention relates to an electrode body and an electrode body manufacturing method and, more particularly, to an electrode body for use in a non-aqueous electrolyte secondary battery and an electrode body manufacturing method.
2. Description of Related Art
As one of non-aqueous electrolyte secondary batteries, there is a lithium-ion secondary battery. The lithium-ion secondary battery is a secondary battery which can be charged and discharged by allowing lithium ions in an electrolyte to move between a positive electrode and a negative electrode which store and release the lithium ions.
Japanese Patent Application Publication No. 2013-080655 (JP 2013-080655 A) discloses a technique regarding a non-aqueous electrolyte secondary battery which makes use of an electrode plate formed by coating an insulation layer on an electrode active material. In the non-aqueous electrolyte secondary battery disclosed in JP 2013-080655 A, a typical sheet-like separator is not used and an insulation layer is used as a separator. In the technique disclosed in JP 2013-080655 A, insulation particles are used as the particles that form the insulation layer.
In the case where the insulation particles are used in the insulation layer of the electrode body as in the non-aqueous electrolyte secondary battery disclosed in JP 2013-080655 A, the insulation layer is formed by directly coating the insulation particles on a negative electrode mixture layer. At this time, the side surface of the negative electrode mixture layer (namely, the side surface of the negative electrode) is kept exposed without being covered with the insulation layer. Therefore, a problem is posed in that if a load is applied to the electrode body, the exposed portion of the negative electrode is short-circuited by making contact with a positive electrode current collector.
FIG. 15 is a view for explaining a problem to be solved by the invention and is a top view illustrating the states of a positive electrode (hereinafter, it may be referred to as a positive electrode sheet) and a negative electrode (hereinafter, it may be referred to as a negative electrode sheet) available before an electrode body is wound. FIG. 16 is a sectional view taken along cut line XVI-XVI in the electrode body illustrated in FIG. 15. As illustrated in FIG. 15, an electrode body 101 includes a strip-shaped positive electrode sheet 110 and a strip-shaped negative electrode sheet 120. The positive electrode sheet 110 and the negative electrode sheet 120 are laminated in a thickness direction.
As illustrated in FIGS. 15 and 16, the positive electrode sheet 110 includes a positive electrode current collector 111 and positive electrode mixture layers 112 disposed on the positive electrode current collector 111 (namely, on the opposite surfaces of the positive electrode current collector 111). A positive electrode mixture layer non-forming portion 114, on which the positive electrode mixture layers 112 are not disposed, is provided in one width-direction end of the positive electrode sheet 110 (namely, at the upper side of the positive electrode sheet 110 illustrated in FIG. 15). Furthermore, the negative electrode sheet 120 includes a negative electrode current collector 121, negative electrode mixture layers 122 disposed on the negative electrode current collector 121 (namely, on the opposite surfaces of the negative electrode current collector 121), and insulation layers 123 disposed on the negative electrode mixture layers 122 and containing insulation particles. A negative electrode mixture layer non-forming portion 124, on which the negative electrode mixture layers 122 are not disposed, is provided in one width-direction end of the negative electrode sheet 120 (namely, at the lower side of the negative electrode sheet 120 illustrated in FIG. 15).
As illustrated in FIG. 16, the positive electrode sheet 110 and the negative electrode sheet 120 are disposed such that the positive electrode mixture layer non-forming portion 114 of the positive electrode current collector 111 and the negative electrode mixture layer non-forming portion 124 of the negative electrode current collector 121 are opposite to each other in the width direction. Furthermore, the width-direction ends of the positive electrode mixture layers 112 are disposed more inward in the width direction than the width-direction ends of the negative electrode mixture layers 122. At this time, the width-direction end 125 of the negative electrode 120 is disposed so as to overlap with the positive electrode mixture layer non-forming portion 114 of the positive electrode current collector 111 when seen in a plan view from the lamination direction of the positive electrode sheet 110 and the negative electrode sheet 120.
In this regard, when insulation particles are used as the insulation layers 123 of an electrode body 101, the insulation layers 123 are formed by directly coating the insulation particles on the negative electrode mixture layers 122. Therefore, the side surface of the end portions 125 of the negative electrode mixture layers 122 (namely, the side surface of the negative electrode 120) is kept exposed without being covered with the insulation layers 123. For that reason, if a load is applied to the electrode body 101 obtained by laminating the positive electrode 110 and the negative electrode 120, the end portions 125 of the negative electrode mixture layers 122 may make contact with the positive electrode mixture layer non-forming portion 114 of the positive electrode current collector 111 (as indicated by an arrow in FIG. 16). This poses a problem in that the positive electrode 110 and the negative electrode 120 are short-circuited.